Antibodies to Epstein-Barr virus and other common viruses (influenza, parainfluenza, rubella, measles, other herpes viruses) will be studied in Burkitt lymphoma, Hodgkin's disease and other lymphatic tumors as well as in nasopharyngeal cancer and systemic lupus erythematosus. The emphasis will be on cancers and chronic diseases of unknown cause in which a defect in cellular immunity may be present. The tests will be carried out intermixed with healthy controls as well as with other types of chronic diseases. When elevated antibody titers are found their specificity and selectivity will be determined, the presence of general vs. selective hyperreactivity analyzed, and the existence of a possible defect in cellular immunity explored by tests of cell mediated immunity to viral specific and non-specific stimuli. The presence or absence of EBV in the throats of these patients and in controls will be tested.